If you want to blend yeasts, do it from the start. Even though it's high gravity, with proper pitch rate it won't take an appreciably longer time then most other beers to accomplish most of it's fermentation. I'd stick with one yeast throughout though, but that's just me. I like having _some_ degree of repeatability in my beer. Ss for bottling, just make sure you rack a little bit of your yeast cake into your bottling bucket. Don't primary at all either, just let it sit on the yeast, let the yeast work.
On Deck: Saison "Jardin d'été" (3rd Gen 3711, Wild bugs, Pale ale malt, wheat, Willamette dry hop)
Primary: Saison "Vomissure de Grenouille" (2nd Gen 3711 from dregs, Pale Ale malt, Crystals and Willamettes)
Secondary: BM45/Spontaneous Bugs Experiment (down to 1.004, and tastes awesome), contemplating what fruit to add.